Workpiece positioning device



1968 JOHNSON, JR 3,415,392

WORKPIECE POSITIONING DEVICE Filed March 16, 1966 IN VEN TOR.

AAA E JOHNSON, J9.

United States Patent Oflice 3,415,392 WORKPIECE POSITIONING DEVICE LaneJohnson, Jr., Carnegie, Pa., assiguor to United Engineering and FoundryCompany, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 16,1966, Ser. No. 534,781 Claims priority, application Great Britain, Mar.31, 1965, 13,747/ 65 4 Claims. (Cl. 21423) ABSTRACT OF THE DISCLOSUREThe disclosure of this invention relates to a slab reheating furnace ofthe type used in the operation of a hot strip mill. The disclosureteaches in combination with an horizontal slab reheating furnace and aroller table arranged below the furnace for conveying slabs away fromthe furnace, the employment of a curved shaped discharge chute arrangedbetween the furnace and the table. The curved surface of the chute isconstructed so that, notwithstanding the differences in size and weightof the slabs, their energy during the descent from the furnace to thetable will be dissipated prior to passing the center of the table. Theinvention also teaches the employment of a pusher ram mounted beneaththe furnace designed to position slabs on the center of the table oncethey have come to rest on the table.

The present invention relates to slab transfer and positioning apparatusfor use in conjunction with a workpiece reheating furnace, say, forexample, with a furnace provided to reheat the workpieces, such asslabs, to a rolling temperature. More particularly, the presentinvention relates to a slab handling and transferring device which willnot only entirely eliminate the destructive potential energy ofdescending slabs but completely eliminate the need of furnishing adevice for dissipating the energy of each slab, as it is allowed toslide down from the elevation of the furnace onto a table arranged belowthe hearth of the furnace.

The rolling of strip by a modern hot strip mill from slabs currently ofthe order of 80,000 lbs. and heavier, measuring in usual :cases to 12.inches x 76 inches x 32 feet, has presented a serious problem intransferring the slabs from the furnace to the table provided totransport slabs to the rolling mill. It was customary in previous mills,which handled much smaller slabs than described above, to arrange thefurnace table approximately 7 feet below the hearth of the furnace. Inthis arrangement slabs were successively pushed from the furnace by apusher means arranged at the entry side of the furnace wherein each slabthen slid down a chute or skid onto the table. In view of the energybuilt up by the slab during its descent, it was customary to provide inconjunction with the table, at the side opposite the furnace, a bumperapparatus engageable by the slab for dissipating its energy and allowingthe slab then to come to rest on the table. Such an arrangement is shownand described on page 626 of The Making, Shaping and Treating of Steel,eighth edition, published by United States Steel Corporation, 1964. Whenthe size and weight of the slabs were increased to the size nowcustomary in operating a modern hot strip mill, it was not surprisingthat serious problems developed with respect to transferring of theslabs from the furnace to the table. In some cases, the energy developedwas so great as to cause damage and breakage to the table and bumperarrangement in addition to resulting in objectionable marking of theslabs.

The seriousness of the problem is indicated by the concentrated effortof the industry to find an acceptable 3,415,392 Patented Dec. 10, 1968arrangement free from energy dissipating problems for transferring aslab from the furnace to the table. Examples of some of the results ofthis effort are illustrated in the following recently issued US.patents: Patent No. 2,515,- 675 which issued to G. Tree on July 18,1950, Patent No. 3,129,829 which issued to H. C. Ferguson on Apr. 21,1964, and Patent No. 3,143,337 which issued to H. A. Rees et al. on Aug.4, 1964. The Ferguson patent, No. 3,129,829, illustrates ratherrealistically the elevational difference between the furnace hearth andthe table wherein an appreciation can be gained of the build-up ofpotential energy in the slab as it slides downwardly from the furnaceonto the table. Of course, in this patent, to reduce the deleteriouseffect of allowing the slab to fall, the slab is actually caught midwayin its descent, rotated and set down on the table.

A still further suggestion to alleviate this acute problem, which ismade Worse by the desire to roll heavier and larger slabs, has been tolower the furnace to eliminate the elevational difference between thefurnace and table and to provide a horizontal slab extractor. In thisarrangement, since there is virtually no difference between theelevation of the hearth and the table, the extractor can be arranged onthe side of the table opposite the furnace and moved into the furnacehearth. The extractor then can lift a slab from the hearth, after whichit will be retracted to dispose the slab on the table. While this designwill, of course, completely eliminate any detrimental consequences ofallowing the slab to'slide from the furnace onto the table, it hascreated other problems which appear to be of considerable magnitude. Oneof these is addressed to the fact that in using an extractor-type slabtransfer, a serious maintenance problem is created because the hydraulicand mechanical components of the device are subject to heavyaccumulation of scale. It is also objectionable since it entailsconsiderable heat losses, as well as requiring that certain extractorcomponents be subjected to the radiation and direct heat from thefurnace for a considerable period of time. Another serious objection isthat the design has eliminated the knuckle joint of the furnace hearth,which affords a significant advantage. This term knuckle has referenceto the intersection where the horizontal portion of the hearth meetswith the inclined portion leading to the table. In employing a knucklejoint, the slabs, should they become inadvertently fused together duringthe reheating process, are automatically separated when the first slabis caused to fall over the joint. In employing a slab extractor device,there is no way of assuring that the two adjacent slabs will notinadvertently adhere to each other when the attempt is made to remove aleading slab.

The present invention eliminates each and every one of the disadvantagesof the arrangements of existing mills, as well as those arrangementswhich have followed, yet retaining the knuckle joint feature. Moreparticularly, the present invention provides for a considerablereduction in the elevational differences between the top of the tableand the hearth surface of the furnace, thus enabling the knuckle jointto be retained, but at the same time permitting a considerable reductionin the potential slab energy and wherein the furnace and table arebridged by a slab transfer member, so proportioned and arranged that forthe entire range of slabs the energy of the slabs built up in theirdescent from the furnace will be dissipated prior to the slabs passingbeyond the table, and preferably as soon as they have fallen asufficient distance onto the transfer member to enable a pusher elementarranged beneath the furnace to engage the one side of the slabs andpush them off the transfer member, if necessary, onto the table wherethe slabs can be centered.

In the preferred arrangement there is provided a customarily constructedslab furnace including a knuckle joint. Between the delivery end of thefurnace and the adjacent slab table, there is provided a slab transportmember made up of several sections. The transport member will have aslab supporting surface configured of an are or an arc and straightsurface, which is nevertheless developed with reference to the range ofslabs to be handled so as to assure that the maximum weighted slab willnot be passed beyond the center of the table, and preferably that theslab will stop after it has slid down the transport member onlysufficiently far enough to enable the reciprocating pusher designed topass through adjacent sections of the transport member to engage theslab and push it onto the table. In addition, there may be provided ameans for raising the pusher up through the adjacent sections of thetransfer member, wherein a portion of the pusher will be positioned toengage the adjacent surface of the slab, in combination with means formoving the pusher towards the table so as to transport the slab onto thetable.

It is a further object of the invention to provide, if desired, anautomatic means for so controlling the traverse of the pusher toautomatically position the slab, notwithstanding a considerablevariation in width, at the center of the table.

The above features and advantages will be better appreciated when thefollowing description is read along with the accompanying drawing, whichconsists of:

An elevational view of a preferred embodiment of the present inventionemployed in combination with a slab furnace for a hot strip rollingmill.

With reference to this drawing, there is illustrated schematically aslab furnace 10, which, as previously noted, can be of ordinaryconstruction and wherein slabs are progressively and successivelyadvanced for reheating to the rolling temperature, say of the order of2250 F. or more. At the discharge side of the furnace there is provideda customary furnace door 11, which is opened and closed by means notshown. Adjacent to the inside wall of the furnace door when the latteris in its closed position, there is a knuckle joint 12 over which eachslab passes prior to discharge from the furnace. Cooperating with thejoint and extending between the furnace and a slab table 13, there isprovided a slab transfer chute or skid 14. This chute, for a reason tobe explained hereinafter, is made in a number of sections and isdesigned to support each slab during its transfer from the hearth of thefurnace to the table 13. As indicated by one of the aforesaid patents,the table consists of a number of motor-driven rollers, only one ofwhich is shown in the drawing, in which connection the drawingillustrates the roller being supported on one end in a girder in acustomary manner. It will be noted with respect to table 13 that thedrawing illustrates a maximum and a minimum slab, which slabs, it shouldbe mentioned, have not as yet been centered on the table.

Turning now to the skid 14, it is important to realize that in thepresent invention the elevation between the top of the rollers of thetable 13 and the hearth of the furnace 10 or the knuckle joint 12 isconsiderably re duced over previous designs incorporating skids. Infact, it is a feature of the present invention to maintain thiselevation only sufficiently to allow the slab to fall down from thefurnace, thus to break any adherence to a previous slab and passsufficiently down the skid so as toenable the pusher to be brought upbehind the slab. As to the other extreme, the slope of the skid isdesigned to prevent any slab from passing beyond the center of thetable. Thus, by this arrangement, the slab is allowed to develop onlysufficient energy by its descent so as to cause a predetermined range ofdownward displacement which is a function of the height and contour ofthe skid 14. In this arrangement, therefore, there is no need of a heavybumper structure on the opposite side of the table, but instead, if suchis deemed desirable, a customary table sideguard can be used or none atall.

It will be noted that the skid 14 takes the form of an arc of a circle,which, in some respects, presents a very desirable tangentialrelationship between the bottom of the skid and the adjacent top surfaceof the rollers so as to provide a smooth transfer action. However,depending on the particular requirements, the configuration of the slabsupporting surface of the skid, as previously noted, may be differentfrom that which is illustrated and may take, for example, the form of acompound curve or a combination of a straight and curve or some otherform. The important matter being that the slab is allowed to generateonly enough energy during its descent to cause it to break away from thefurnace and move away from the door, but not sufficient to allow theslab to develop such a force as to allow it to pass beyond the center ofthe table.

It was previously noted that the skid 14 is made in sections. This is toprovide two or more separations between them and to enable two or moreslab pusher heads 17 to'be raised between the skid sections, after whichthe heads can be traversed towards the table to push the slab off theskid, should the slab have come to rest thereon, and in any event, ontothe table 13. As shown the pusher heads 17 are an integral part of a ram18 which is provided with a rack 19 that meshes with a pinion 20, thepinion being driven by a motor, not shown. The ram 18 is raised in anoperative position by a piston cylinder assembly 21 which is connectedto the ram by a pair of rollers 26 and 27. It is important to note thatthe entire slab pusher assembly is located beneath the furnace where itwill be free from scale and radiant heat.

Returning now to the two maximum and minimum slabs illustrated on thetable 13, it is to be appreciated that the represented position of thetwo slabs are meant to indicate the positions they will assume aftertheir energy has been dissipated by the friction generated between theslab and the skid 14. Once so positioned the ram head 17 will beadvanced to move the slab in the center of the table. In this connectionthe drawing illustrates in phantom a head 17 in its pushing positionagainst the smaller slab.

Another advantage of the present invention, not previously noted, isdiscernible in referring to the drawing in comparison with the olderdesigns employing skids. It will be observed that the reduction inelevation between the furnace and the table in the present inventionwill re- 'sult in a lessening of the tilting of the slab as it fallsonto the skid which will reduce heat losses since the furnace door willnot need to be opened as far. In the illustrated arrangement theelevational difference between the table and the hearth is approximatelyfifteen inches, the arrangement being designed to handle a range ofslabs measuring 20 inches x 5 inches x 32 feet in one case and up to 76inches x 10 inches x 3.2 feet in another case. The heaviest slab willweigh approximately 83,600 lbs.

For the above, it can be seen that the present invention allows themaintaining of the knuckle joint of the furnace, thereby enabling arealization of the advantages that flow from the employment of the jointwhich were previously noted; the slab is stopped after a minimum travelsubsequent to its discharge from the furnace, which travel is controlledto be just far enough to allow a pusher element to engage the adjacentside of the slab to effect a transfer from the furnace to the table.Thus, the energy created in the descent of the slab, while not entirelyeliminated, is not allowed to damage the equipment, but used to itsfullest advantage in carrying out the primary object of transferring theslab. This is done in such a way that there is no necessity of providingmeans either p to strengthen the table itself or in providing theelaborate bumper mechanism to dissipate the energy of the slab createdby its descent.

The present invention is capable of being adapted for other uses andbeing modified and varied to meet the specific requirement withoutdeparting from its scope.

In accordance with the provisions of the patent statutes, I haveexplained the principle and operation of my invention and haveillustrated and described what I consider to represent the bestembodiment thereof. However, I desire to have it understood that withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. In combination with a furnace and a table spaced from said furnaceand at a lower elevation therefrom for receiving workpieces of variousparameters and conveying them away from the furnace,

a workpiece transfer means arranged between said furnace and table fortransferring workpieces from said furnace directly to said table,

a workpiece pushing means for moving a workpiece transferred by saidtransfer means from a point below the upper end of said transfer meansto a predetermined point on said table,

said transfer means having a workpiece engaging surface so constructedand arranged relative to the varying parameters of the workpieces andthe difference in elevation of the furnace and table that the energy ofthe descending workpieces will be dissipated prior to passing saidpredetermined point on said table and within an area defined by said twopoints.

2. In combination with a furnace and a table in accordance with claim 1wherein said furnace has a discharge opening,

a door for closing said opening after a workpiece has passedtherethrough,

a knuckle joint in said furnace over which each workpiece pa'ssesimmediately prior to passing through said opening,

said table made up of spaced-apart rollers having their axes in a planeparallel to the longitudinal axis of the furnace,

wherein said workpiece transfer means comprises a number of spaced-apartsections, and wherein through the openings formed thereby said pushingmeans extends for engagement with a workpiece.

3. In combination with a furnace and table in accordance with claim 2,wherein said pushing means are located beneath said furnace so as not tobe subject to deposits of scale that form on the workpieces andcollected by said transfer means, and

wherein said pushing means includes upright workpiece engaging fingersconstructed to pass into the openings formed by the sections of saidtransfer means, including means for advancing said pushing means towardsand away from said table and separate means for raising and loweringsaid pushing means.

4. In combination with a discharge station and a table in accordancewith claim 2, wherein the construction of said workpiece engagingsurfaces of said transfer means takes the form substantially of an arcof a circle, the lower portion of which is tangentially disposedrelative to the top of the rollers of said table.

References Cited UNITED STATES PATENTS 1,127,315 2/1915 Swindell 214-481,467,541 9/1923 Ford 193-1 X 2,880,844 4/1959 Vogeli 198-26 2,954,1159/1960 Engleson et a1. 198-1221 3,243,059 3/1966 Kalberkamp 214-26ROBERT G. SHERIDAN, Primary Examiner.

US. Cl. X.R. 1931; 198-59

